1. Field of the Invention
The present invention relates to a multilayer ceramic electronic component and a manufacturing method thereof, and more particularly relates to the structure of external terminal electrodes provided in a multilayer ceramic electronic component and a method for forming the external terminal electrodes.
2. Description of Related Art
In recent years, the market for compact portable electronic devices, such as mobile phones, notebook personal computers, digital cameras, and digital audio devices, has been expanded. In the field of portable electronic devices, reduction in size and improvement in performance have been simultaneously advanced. Many multilayer ceramic electronic components are mounted in one portable electronic device, and therefore, the multilayer ceramic electronic components are also required to be reduced in size and to be improved in performance. For example, a multilayer ceramic capacitor is required to be reduced in size and to be increased in capacity.
As means for reducing the size of a multilayer ceramic capacitor and for increasing the capacity thereof, a decrease in thickness of ceramic layers is effective, and in recent year, ceramic layers having a thickness of approximately 3 μm have been practically used. A further decrease in the thickness of ceramic layers has been attempted but as the thickness of the ceramic layers is decreased, short-circuiting is liable to occur between internal electrodes, and as a result, it becomes disadvantageously difficult to ensure the quality.
As another means, it has been conceived to increase the effective area of any internal electrode. However, when mass production of multilayer ceramic capacitors is performed, in consideration of errors in stacking ceramic green sheets and/or cutting a laminate of ceramic green sheets, a side margin between the internal electrode and a side surface of a ceramic base body and an end margin between the internal electrode and an end surface of the ceramic base body must be ensured to a certain extent. Hence, an increase in effective area of the internal electrode is restricted.
In order to increase the effective area of the internal electrode while providing predetermined margins, the area of the ceramic layer must be increased. However, an increase in the area of the ceramic layer within a predetermined dimensional standard is restricted, and additionally, the thickness of an external terminal electrode disturbs the increase in the area of the ceramic layer.
Heretofore, external terminal electrodes of a multilayer ceramic capacitor are formed by applying a conductive paste to end portions of a ceramic base body, followed by firing. As a method for applying a conductive paste, the method in which an end portion of the ceramic base body is immersed in a conductive paste bath and is then removed therefrom is primarily performed; however, the conductive paste tends to adhere thick to a central part of the end surface of the ceramic base body due to the viscosity of the conductive paste in this method. Hence, the thickness of the external terminal electrode is partly increased (for example, in particular, to more than approximately 30 μm), and in order to offset the above increase, the area of the ceramic layer must be decreased.
In order to solve the above problem, a method in which the external terminal electrode is directly formed by plating has been proposed (for example, see International Publication No. WO 2007/049456 Pamphlet). According to this method, a plating film is deposited using exposed portions of internal electrodes located at an end surface of a ceramic base body as nuclei, and as the plating film is grown, the exposed portions of the internal electrodes adjacent to each other are connected to each other. Hence, by this method, compared to the method using a conductive paste, a thin and flat external terminal electrode can be formed.
However, the adhesive effect of glass, which was obtained in the method using a conductive paste, cannot be obtained in the plating method, and there has been a problem in that a bonding force of the plating film, that is, the external terminal electrode, to the ceramic base body is not sufficient.